The present invention relates to an illumination module for a coordinate measuring machine for measuring a workpiece by means of an optical sensor, wherein the illumination module comprises a main body having a sensor side and a workpiece side, wherein the illumination module comprises on the main body at least one illumination arrangement for illuminating the workpiece, and wherein the at least one illumination arrangement has an emission characteristic with a specific emission angle and a light intensity profile within the emission angle.
In accordance with a second aspect, the present invention relates to a coordinate measuring machine for measuring a workpiece by means of an optical sensor.
Coordinate measuring machines are generally known in the prior art. They serve to check workpieces in the context of quality assurance, for example, or to determine the geometry of a workpiece completely in the context of so-called “reverse engineering”. Furthermore, diverse further application possibilities are conceivable.
In such coordinate measuring machines, various types of sensors can be employed in order to set the coordinates of a workpiece to be measured. By way of example, sensors that effect tactile measurement are known for this purpose, such as are sold for example by the applicant under the product designation “VAST”, “VAST XT” or “VAST XXT”. In this case, the surface of the workpiece to be measured is probed with a probe pin whose coordinates in the measurement space are continuously known. Such a probe pin can also be moved along the surface of a workpiece, such that in such a measuring process in the context of a so-called “scanning method” a multiplicity of measurement points can be detected at defined time intervals.
Furthermore, it is known to use optical sensors which enable the coordinates of a workpiece to be detected contactlessly. One example of such an optical sensor is the optical sensor sold by the applicant under the product designation “ViScan”.
The sensors can then be used in various types of measurement set-ups. One example of such a measurement set-up is the product “O-INSPECT” from the applicant. In such a machine, both an optical sensor and a tactile sensor are used to carry out different inspection tasks on one machine and ideally with a single clamping of a workpiece to be measured.
Sensor systems having optical sensors are becoming increasingly important in coordinate measuring technology. In this case, optical sensors are distinguished in particular by a high speed of the measuring process. In this way, many inspection tasks for example in medical technology, plastics technology, electronics and precision mechanics can be carried out. It goes without saying that, furthermore, various other set-ups are also conceivable.
Traditionally, the optical sensor head or the optical sensor is connected to a carrier system that supports and moves the optical sensor system. Various carrier systems are known in the prior art, for example gantry systems, stand, horizontal arm and arm systems, and all kinds of robot systems. In this case, the carrier systems can furthermore have system components that enable the sensor head to be positioned as flexibly as possible. One example thereof is the rotary-pivoting articulated joint from the applicant sold under the designation “RDS”. Furthermore, various adapters can be provided in order to connect the different system components of the carrier system among one another and to the sensor system.
Furthermore, in coordinate measuring technology it is customary that different types of illumination can be applied when measuring objects. The corresponding optical sensors then have a video camera and/or a photographic camera and a corresponding illumination for the workpiece. Furthermore, a fixed imaging optics is provided, which images the workpiece to be measured onto the camera or the optical sensors of the camera. In this case, specific optical sensors with fixedly integrated illuminations and imaging optics are generally provided for each application or each type of measurement.
By way of example, the document EP 0 362 625 A2 shows an exchangeable front optics for an optical probe head. Said front optics is designed for a specific working distance and a specific type of illumination. Furthermore, it comprises the entire lens that images light rays reflected from the workpiece onto the optical sensor.
However, on account of the optical elements for imaging, such a front optics is relatively heavy and has a relatively large volume. Furthermore, such a front optics can be used only for one specific application, i.e. at one specific working distance and for one specific type of illumination.
Furthermore, the documents EP 0 385 262 A2 and EP 1 373 827 B1 likewise specify illumination devices for coordinate measuring machines which firstly comprise imaging optics and secondly comprise illumination elements of relatively complex design, for example pivotable or movable illumination elements, in order to set the illumination to different wavelength distances. However, this also results in a relatively complex construction of such illumination elements and a possibly higher weight and volume, which, on account of the higher inertia associated therewith, makes it more difficult to regulate the optical sensor head, particularly during rapid measuring processes.
Depending on the workpiece to be examined and the measuring method employed by means of the optical sensor, the workpiece can be illuminated in various ways. In this case, by way of example, a working distance at which the measuring process is performed can vary. Furthermore, an illumination at different angles of incidence on a surface of the workpiece may be desired under certain circumstances. Therefore, in practice, either illumination modules can be exchanged or an illumination module comprises a plurality of alternately switchable light sources in order to provide the different types of illuminations. However, such arrangements firstly make an illumination module heavier and secondly increase the costs of an illumination module. However, it is desirable, in principle, to be able to provide more types of illuminations by means of an illumination module, i.e. illuminations at different working distances and/or at different angles of incidence.